Feature request: public reflection interface to obtain GLSL uniform constant initializer values

[slime73]

Desktop GLSL allows initializing unbuffered uniform variables to a constant value directly in shader code.

As far as I can tell (and please let me know if I'm wrong), glslang's reflection interface doesn't expose those values anywhere, but it does internally detect them because it correctly errors when a uniform is initialized to a non-constant value on desktop GLSL and when a uniform is initialized to a constant value in GLSL ES.

I'd really like a way to obtain their values (and whether they've been explicitly initialized), through glslang's APIs. I have an existing tool with desktop GLSL shaders written for it by a large number of people, and I want to use glslang's SPIRV output capabilities combined with SPIRV-Cross to translate those shaders to other graphics APIs, but not every shader will be able to be fully ported without having a way to identify those values, and I wouldn't be able to tell users when their shader wouldn't work either, unless I restrict myself to GLSL ES.

[slime73]

I now see that #1588 exists - if after applying that change I can parse the constant values from spirv generated with glslang, I think that will be sufficient for my purposes.

[slime73]

The above PR was merged. Thanks!